1. Field of the Invention
The present invention relates to a playback apparatus for playing back music and a power-saving method.
2. Description of the Related Art
Audio players that record digital audio data on a solid-state memory, a disk, etc. and play back the data have been used widely in recent years. The digital audio data is compressed by digital data compression technology. For example, all songs of one CD can be stored in a flash memory card whose storage capacity is much smaller than that of the CD, and data of a plurality of CDs can be compressed and stored in a CD-R and reproduced therefrom.
Players using a flash memory card include a portable player having a slot that is adaptable to an SD card, Smartmedia, compact flash and the like. Players using a CD-R include a portable player having both a CD player function and a playback function such as MP3 and WMA and a DVD player having an MP3 playback function.
Some audio players are adaptable to a variety of audio formats. They are able to select and reproduce any music that is stored in the audio formats.
However, some audio players require a large amount of power consumption in decoding music data (including decompressing music data) according to the type of audio format. If a battery-powered portable player plays back music without taking consideration a difference in power consumption between different audio formats, a battery will be exhausted at once. If, in particular, music that is stored in audio format requiring a large amount of power consumption is played back with a small amount of remaining charge of a battery, the battery will be exhausted in a very short time.
In order to resolve the above problem, a technique to prevent a battery from being exhausted quickly and lengthen playing time while the remaining amount of charge of the battery is small is desired.
Jpn. Pat. Appln. KOKAI Publication No. 7-065507 discloses a technique to lengthen the lifetime of a battery in a portable disk playback apparatus. However, this technique aims at lengthening the lifetime of a battery used as a driving power supply by stopping a servo control operation during the stoppage of readout of data from a recording medium and does not refer to the problem of battery exhaustion due to an audio format requiring a large amount of power consumption.